Police departments across the country took steps Friday to protect their officers after shootings in Dallas Thursday left five police officers dead and seven wounded.

New York Police Department increased security at precincts across the city and directed that patrolling be done in pairs rather than by individual officers, said Officer Brian Magoolaghan, a department spokesman. A memorandum issued to New York police early Friday urged officers to "maintain a heightened level of awareness" and staying vigilant, Magoolaghan said.

A host of other city police departments across the country directed that officers patrol in pairs while on foot or in cars for greater security after what happened in Dallas. According to police and media reports, those cities include Philadelphia, Seattle, Las Vegas and Cleveland.

The police chief of Burlington, Vt., Brandon del Pozo said that when he woke up Friday morning to news of the Dallas shootings, "I was literally shaking. It was beyond words."

He also directed his officers to conduct foot patrols in pairs until the threat of copycat killings passed.

Dallas Police Chief David Brown told reporters Friday that a sniper involved in the shootings had spoken with a crisis negotiator before being killed during a stand-off Thursday night and confessed to wanting to "kill white people, especially white officers."

Meanwhile, in Orlando — the scene of the worst mass shooting in U.S. history last month when a gunman killed 49 people at a gay night club before being shot by police — the city police department said on Twitter it had received a "vague threat" Friday in the wake of the Dallas shootings and was investigating it.

Brown said the gunman was motivated by police-involved shootings across the country where black civilians have been killed.